stabilizer.h

// stabilizer.h

/*!\file 
defines the Stabilizer class */

#ifndef STABILIZER_H
#define STABILIZER_H

#include <iostream>
#include <vector>
#include <cassert>
#include "loccliff.h"

#include <ext/hash_set>
#ifndef SWIG
using __gnu_cxx::hash_set;
#endif
// See note at top of file graphsim.h in case of problems compiling
// the preceding lines.


#ifdef SWIG
struct QState;
#else
extern "C" {
   // The following struct declaration is quoted in verbatim from Scott
   // Aaronson's CHP program. (Scott, I hope, you don't mind.) It is used
   // here to implement the functionality of comparing a stabilizer state
   // in CHP with a state in graphsim. This is used to compare the action
   // of the two programs to ensure correctness.
   struct QState
   {
      long n;         // # of qubits
      unsigned long **x; // (2n+1)*n matrix for stabilizer/destabilizer x bits (there's one "scratch row" at
      unsigned long **z; // (2n+1)*n matrix for z bits                                                 the bottom)
      int *r;         // Phase bits: 0 for +1, 1 for i, 2 for -1, 3 for -i.  Normally either 0 or 2.
      unsigned long pw[32]; // pw[i] = 2^i
      long over32; // floor(n/8)+1
   }; 
}
#endif //SWIG

//forward declarations, definition in graphsim.h:

typedef unsigned long VertexIndex;
struct QubitVertex;
class GraphRegister;

//! A stabilizer describing a quantum state.
/* This class is used at the moment only by GraphRegister::print_stabilizer and for
the compare method (when comparing with CHP). */
struct Stabilizer {
   VertexIndex numQubits;
   vector<vector<LocCliffOp> > paulis;
   vector<RightPhase> rowsigns;
   vector<VertexIndex> vtxidx;
   Stabilizer (const VertexIndex numQubits_);
   Stabilizer (const GraphRegister& gr, const hash_set<VertexIndex>& qubits);
   Stabilizer (QState * qs);
   void add_row (unsigned target, unsigned addend);
   void conjugate (unsigned row, unsigned col, const LocCliffOp trans);
   void conjugate_column (unsigned col, const LocCliffOp trans);
   void print (ostream &os = cout) const;
   bool compare (const Stabilizer &diag);
};

#endif //STABILIZER_H